Breathable and elastic fabric lamination

ABSTRACT

A flexible, breathable, stretchable fabric laminate is formed from two knit pile fabrics, one having exposed hook-engageable fiber loops and the other providing a skin contact surface. The grounds of both knits include elastomeric yarns, and the fabrics are bonded together at their technical faces, with adhesive in contact with both pile yarns and elastomeric ground yarns of each knit fabric but covering only portions of the laminate to leave other portions air-permeable.

RELATED APPLICATIONS

This U.S. Patent Application claims priority under 35 U.S.C. §120 fromU.S. Patent Application 61/414,324, filed on Nov. 16, 2010. Thedisclosure of this prior application is considered part of thedisclosure of this application and is hereby incorporated herein byreference in its entirety.

TECHNICAL FIELD

This invention relates to forming breathable and elastic fabriclaminates from multiple fabric layers, and to such laminates.

BACKGROUND

Some fabrics having multiple layers are formed as knit spacer fabrics,in which two knit fabric layers are knit in parallel so as to havethreads extending between the layers, so as to give the overall fabricmore loft. Such fabrics may be produced, for example, on a weft knittingmachine having two sets of needles that produce two distinct layers offabric that are held together by tucks, or on double bar raschel warpknitting machines. Other multi-layer fabrics are formed by laminating(such as by adhesive) two pre-formed fabric layers.

Multi-layer fabrics have many uses, including in the medical, appareland sports markets for applications in which one of the fabric layers isto be placed against skin. In such applications it is desirable that thefabric layer to be placed against skin be comfortable to the touch. Forapplications in which the fabric is to engage with touch fasteners, theouter layer may be constructed to be hook engageable. Such products areuseful in medical and sports markets for applications such as straps,which may support medical devices on a patient, or in braces that may bewrapped around body parts, such as elbows or knees as a support.

For some applications, hook-engageable loop fabrics are laminated tofoams or Neoprene polychloroprene to add comfort, stretch, orcompress-ability. Many of these composite fabrics have poor airpermeability and do not allow sweat and heat to move quickly away fromthe skin. In prolonged skin contact situations, bacteria can develop inthis wet environment, resulting in odor, possible skin infections ordermatitis. In some products, the fabric used on the inside of thelaminate in contact with the skin is an inexpensive tricot knit fabric.

In some laminates, such as Breath-O-Prene®, a hook-engageable fabric islaminated to one side of a Neoprene polychloroprene, and an inexpensivetricot fabric is laminated on the other side. The Neoprenepolychloroprene in this case is perforated in an attempt to promote airpenetration and moisture movement. Silver-Tec® brand laminate is similarto a Neoprene polychloroprene laminate and contains silver to provideanti-microbial properties. Some other straps, such as the Futuro™ brandstraps made by 3M, feature an open, net-like fabric such as in thePowerstretch-Rx® product available from Polartec. This fabric is anon-hook-engageable knit fabric that is said to have moisture-releasingproperties. Other brace straps, like the Futuro® Infinity precision-fitbraces, advertise enhanced breathability and anti-microbial support.These laminates are foam laminates with a soft interior skin contactfabric laminated to a foam core, then laminated to an outer layer ofhook-engageable loop material with holes on one side of the laminate,such as formed by knitting the material with multiple tucks on oneneedle, that allow for some air and moisture transport.

Single-knit jersey fabrics are generally inexpensive and found in suchthings as underwear and T-shirts. Due to their interconnected loopstructure, knit materials in general can be deformed or stretched byelongating individual stitches, even when the fabric is knit of yarnsmade of non-elastomeric fiber materials. To provide a greater degree ofstretch and stretch recovery, elastomeric yarns may be knit into afabric. One type of elastomeric yarn in common use is spandex. Spandex,sometimes sold under the trade name LYCRA®, is a manufactured fiber of along-chain synthetic polymer containing at least 85 percent segmentedpolyurethane. The polyurethane is prepared from a polyether glycol, amixture of diisocyanates, and a chain extender and then melt-spun,dry-spun or wet-spun to form the spandex fiber. Another type ofelastomeric yarn is polybutylene-terephtalate (PBT) yarn, a highlyelastic, friction-texturized polyester yarn available from Swicofil AGTextile Services of Emmenbruecke, Switzerland.

Knitting spandex yarns together with non-elastomeric yarns in a jerseyknitting process is sometimes referred to as “plating,” in which thenon-elastomeric yarn and the bare spandex yarn are kept in a parallel,side-by-side relation throughout the knit, with the relation between thetwo yarns controlled such that the spandex material is always kept onone side of the non-elastomeric yarn. In plush or pile materials, thespandex yarn is generally kept away from the technical face of thefabric (i.e., the side opposite the raised pile), so as to present thetypically more attractive and comfortable non-elastomeric yarn materialat the technical face and to protect the spandex yarn fibers fromsnagging. Spandex yarns may also accept dye differently than other yarnmaterials, resulting in unacceptable color variations if exposed on thefabric surface. Stretchable pile fabrics may be made in a three endknitting process, meaning that three separate yarns are brought into themachine and knit together to form the fabric: a non-elastomeric groundyarn, an elastomeric ground yarn, and a pile yarn. As knit, thenon-elastomeric and elastomeric ground yarns are generally limited tothe ground of the fabric, and the pile yarns extend out of the fabric toform discrete loops, which in some cases are cut or shaved afterprocessing to form a bed of fiber ends. The non-elastomeric andelastomeric ground yarns may be plated to keep the elastomeric yarnsaway from the technical fabric face while being knit into the fabric, ormay be “laid in” or tucked into the knit structure using needleselection cams, to trap the elastomeric yarns between thenon-elastomeric ground and pile yarns.

Some knit materials are formed as circular knit materials, meaning thatthey are initially knit as a tube on a machine in which the knittingneedles are organized into a circular knitting bed. The needles aresequentially activated about the circular bed, such as by a cam surfaceacting against butt ends of the rotating set of needles, to lift andaccept a yarn fed from a spool into a yarn carrier plate, to form aspiral row of stitches about the end of the tube. Such a process is alsoreferred to as circular weft knitting. To circular knit a three endstretchable plush or pile fabric, the non-elastomeric ground yarn, theelastomeric ground yarn and the pile yarn are each fed separately torespective holes or slots in the carrier plate. In particular, theelastomeric yarn is kept separate from the non-elastomeric ground yarnuntil the point of introduction to the needles, so as to maintain thestrict positional relation of non-elastomeric and elastomeric yarns, inorder to keep the spandex material from being exposed, or “grinningthrough” the technical face of the fabric. In some cases, such as onsome Orizio machines made by Orizio SRL, Brescia, Italy, the elastomericyarn is run outside of the carrier plate, and guided into the needlebefore it closes by an outside guide roll. Circular knitting machinesare also available from Vanguard Supreme, a division of the MonarchKnitting Machinery Corporation, in Monroe, N.C.

Improvements in stretchable laminate constructions and methods of makingthem will hopefully result in further advances in comfort andusefulness, as well as in reductions in costs.

SUMMARY

One aspect of the invention features a flexible, breathable, stretchablefabric laminate that has first and second stretchable fabric layers. Thefirst stretchable fabric layer is in the form of a first knit fabricthat has ground yarns and pile yarns. The pile yarns formhook-engageable fiber loops exposed on an outer surface of the fabriclaminate. Both portions of ground yarns and portions of pile yarns arepresent at a technical face of the fabric. The second stretchable fabriclayer is bonded directly to the first fabric layer by an adhesive, andis in the form of a second knit fabric having both ground yarns and pileyarns. Like the first stretchable fabric layer, the second stretchablefabric layer has a technical face at which both portions of ground yarnsand portions of pile yarns are present. At least one of the first andsecond knit fabrics, and in some cases both, is a circular knit fabric,and the ground yarns of both the first knit fabric and the second knitfabric include elastomeric yarns. The first and second fabric layers arebonded together at their technical faces, such that the adhesive is incontact with both pile yarns and elastomeric ground yarns of each knitfabric.

Preferably, the adhesive covers no more than about 70 percent of eitherfabric layer, leaving adhesive-free areas of the laminate.

In embodiments in which both knit fabrics are circular knits, themachine knit directions of the first and second knit fabrics may bealigned in the laminate.

In some laminates, the first knit fabric is relatively more hydrophilicthan the second knit fabric, such as to aid in evaporating moisturethrough the laminate.

In some configurations, the ground yarns of the first knit fabricinclude both elastomeric yarns and texturized, non-elastomeric yarns.The texturized, non-elastomeric yarns may be nylon yarns, for example.In some knits, each elastomeric yarn follows a common path through thefirst knit fabric with a corresponding texturized yarn. The elastomericyarns may be bare, non-wrapped yarns that are knit in with thetexturized yarns. For some applications, the texturized, non-elastomericyarns are also present at the technical face of the first knit fabric.

In some examples, essentially all of the ground yarns of at least one ofthe first and second knit fabrics are elastomeric yarns.

The laminate preferably has a basis weight of less than about 12 osy(400 gsm), and an air permeability, measured in accordance with ASTMD737-04, of at least 40 cfm per square foot (12 meters/min), or in somecases at least 75 cfm per square foot (22 meters/min).

The laminate preferably has an overall thickness that is less than about0.15 inch (3.8 mm).

In some examples the ground yarns of the first knit fabric includetexturized nylon yarns, and the ground yarns of the second knit fabricinclude texturized polyester yarns. The texturized polyester yarns ofthe ground yarns of the second knit fabric may be chosen to be ofnon-circular cross-section.

For some applications, such as those in which the laminate is to be worndirectly against skin, the pile yarns of the second knit fabric form acut or broken loop pile on an exposed side of the laminate opposite theouter surface on which the hook-engageable fiber loops are exposed. Thesecond fabric preferably has, for such applications, an exposed skincontact surface configured to provide a kinetic friction coefficient ofat least 0.3.

In some embodiments, the first stretchable fabric layer includes astretchable binder, such as an acrylic, within the ground of the firstknit fabric.

Another aspect of the invention features a method of forming abreathable fabric laminate from fabrics of differing properties. Themethod includes providing first and second knit fabrics having technicalfaces at which portions of both pile fibers and elastomeric groundfibers are present, one of the fabrics being relatively more hydrophilicthan the other fabric and at least one of the fabrics being a circularknit fabric; applying an adhesive to the technical face of at least oneof the knit fabrics; and then bonding the technical faces of the fabricstogether to form a breathable laminate.

Preferably the adhesive is applied such that it occupies no more thanabout 70 percent of the area of the technical face to which it isapplied. The adhesive may be applied by a dot gravure process, forexample.

In some examples, each of the first and second knit fabrics defines amachine knit direction, and the technical faces are bonded together withthe machine knit directions of the first and second knit fabricsaligned.

In some embodiments, providing the first knit fabric includes circularknitting the first knit fabric from elastomeric ground yarns,non-elastomeric texturized ground yarns, and pile yarns. Knitting thefirst knit fabric may involve causing each elastomeric ground yarn tofollow a respective path through the first knit fabric with acorresponding texturized ground yarn. For example, during knitting eachelastomeric ground yarn and its corresponding texturized ground yarn maytogether feed out of a common hole in a respective yarn carrier plate.

In some examples, providing the first knit fabric includes applying anelastomeric binder that impregnates the ground of the first knit fabric.

Another aspect of the invention features a flexible, stretchable fabriclaminate having a first stretchable fabric layer in the form of acircular jersey knit fabric comprising ground yarns and pile yarnsforming hook-engageable fiber loops exposed on an outer surface of thefabric laminate, and a second stretchable fabric layer bonded directlyto the first fabric layer by an adhesive. Preferably, the adhesivecovers no more than about 70 percent of either fabric layer, leavingadhesive-free areas of the laminate.

Yet another aspect of the invention features a flexible, breathable,stretchable fabric laminate to be worn against skin. The laminateincludes a first stretchable fabric layer in the form of a first fabrichaving ground yarns and pile yarns, with the pile yarns forminghook-engageable fiber loops exposed on an outer surface of the fabriclaminate. The laminate also includes a second stretchable fabric layerbonded directly to the first fabric layer by an adhesive that covers nomore than about 70 percent of either fabric layer, leaving adhesive-freeareas of the laminate. The second fabric layer is in the form of asecond fabric having an exposed skin contact surface. The first knitfabric is relatively more hydrophilic than the second knit fabric, andthe exposed skin contact surface of the second fabric is configured toprovide a kinetic friction coefficient of at least 0.3. In some cases,at least one of the first and second knit fabrics is a circular knitfabric.

Another aspect of the invention features a method of forming a circularknit pile fabric. The method includes feeding a multi-filamentnon-elastomeric yarn from a first spool into an aperture defined in ayarn carrier plate that guides the non-elastomeric yarn sequentially toa series of knitting needles spaced about a circular needle array; whilefeeding an elastomeric yarn from a second spool to the yarn carrierplate, such that a fabric is knit to have a ground comprising both thenon-elastomeric yarn and the elastomeric yarn; while feeding a pile yarnfrom a third spool into a pile yarn aperture defined in the carrierplate, such that the pile yarn is delivered to the knitting needles toform a pile extending from a technical back of the knit fabric. Theelastomeric yarn is fed to the carrier plate such that the fabric groundis knit to have a technical face, opposite the pile, in which theelastomeric yarn is exposed in greater proportion than thenon-elastomeric yarn.

Various examples of the proposed fabrics and methods described hereincan provide particularly useful combinations of permeability,hook-engageability, skin-friendliness and elasticity, as well as otherproperties (such as bacteria resistance) in some configurations. Theconstruction of both fabrics, the adhesive or other bonding meansselected, and the lamination technique, can cooperate to provide goodair permeability, delamination strength, moisture wicking, durability towashing, hook-engageability and biocompatibility. Knitting one or bothfabrics to have elastomeric as well as pile yarns present on thetechnical faces that are bonded together can help to further secure boththe pile yarns and the elastomeric yarns in the lamination process. Useof circular jersey knit fabrics in some versions of such laminates canhelp to provide particularly cost-effective, comfortable solutions forproducts to be held or worn against skin.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic illustration of a fabric laminate material, inside cross-sectional view.

FIG. 2 is an enlarged photograph of a fabric laminate material, in sideview.

FIG. 3 is a schematic illustration of a knit ground structure.

FIG. 4 shows yarn paths through a three yarn knit material, with pileyarn included in every course and an elastomeric ground yarn included inevery other course.

FIG. 5 illustrates a machine and process for forming a fabric laminatefrom two knit materials.

FIGS. 6 and 7 show a yarn feeder assembly in use in a circular knittingmachine.

FIG. 8 shows a yarn feeder assembly as viewed from below.

FIG. 9 is a highly enlarged side view of a laminate, showing discreteamounts of adhesive bonding two knit fabrics together.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring first to FIG. 1, a flexible, breathable fabric laminate 10includes a first stretchable fabric layer 12 in the form of a knitfabric 14 that has ground yarns and pile yarns forming hook-engageablefiber loops 16 exposed on an outer surface of the fabric laminate, and asecond stretchable fabric layer 20 in the form of a second knit fabric30 having a technical face 24 bonded directly to the technical face 18of the first fabric layer 12 by an adhesive 22. As will be discussedfurther below, elastomeric yarns are included in the ground yarns ofboth of the knit fabrics, so as to make each fabric elasticallystretchable.

Both knit fabrics 14,30 may be jersey pile knits that are knit to havesections of pile fibers present on technical faces 18,24 along with atleast some elastomeric ground yarns. Either or both fabrics may becircular knit fabrics. The adhesive 22 is arranged in discrete regionsthat together cover no more than about 70 percent of either fabriclayer, leaving adhesive-free areas of the laminate 10. Adhesive 22 is incontact with both portions of the pile yarns and portions of theelastomeric ground yarns of each fabric at their respective technicalfaces.

Referring also to FIG. 2, the laminate 10 has an overall thickness, asmeasured in accordance with ASTM D1777 Section 7, Volume 7.01, with athickness gauge modified for loop textiles with a two-inch (50 mm)diameter foot and a contact force of 31 +/−3 grams, supplied by B C AmesInc, of Melrose Mass., USA, as Model no ABD-2600N DIG. IND, as perdrawing number 07-0113, of about 0.095 inch (2.4 mm). Overall fabricthickness for many applications, measured in this manner, is preferablybetween about 0.07 and 0.15 inch (2 and 4 mm). Some loss of thicknesscan occur due to pressures applied in lamination or during winding. Thismay be more evident on lighter weight laminates with less crushresistance. The lamination of the two materials in the manner discussedherein provides a finished product with a relatively uniformlyhook-engageable side 32, and a comfortable cut-pile or broken loop side34. The technical faces of both materials are intimately bonded directlytogether by discrete, spaced-apart amounts of adhesive that flows intointer-fiber interstices of both fabrics without fouling either the loops16 or the cut-loop fibers forming the skin contact surface. Furthermore,the hydrophobic-hydrophilic nature of the laminate tends to pullmoisture away from surface 34 and toward surface 32, where itevaporates. The nature of the fabric grounds, even with the inclusion ofelastomeric yarns as discussed below, results in a very air-permeableproduct.

Referring back to FIG. 1, first fabric layer 12 is a knit fabric 14formed primarily of hydrophilic yarns that help pull moisture frominside the laminate, for evaporation from the exposed outer surface ofthe laminate. An example of such a fabric 14 is a circular knit loopmaterial knitted from three yarns: a 40/13 texturized nylon ground yarn,a 70 denier monofilament spandex ground yarn having an elongation of atleast 475 percent at break, and a 70/12 nylon pile yarn. (As usedherein, an X/Y description of a yarn signifies a yarn with

X total denier and Y filaments, such that the ratio X/Y denotes thedenier per filament, or dpf.) The pile and ground yarns are introducedat every feed point, and the spandex ground yarn at every other feedpoint, with the spandex yarns fed through the same ground feed hole asthe nylon ground yarn at every other carrier plate, such that everyother row of stitches includes a spandex filament. The spandex yarns canbe run into even fewer carriers, such as every third or fourth carrierplate, to produce fabrics of lower elasticity, or into every carrierplate if desired. Pile yarn can also be added every stitch, every otherstitch, or as frequently as desired to provide a desired fabric weightand cost.

FIG. 3 illustrates a jersey knit ground structure in which every row ofstitches contains both a spandex monofilament 40 and a multi-filamentground yarn 42. The pile yarns are omitted from this illustration, forclarity. This figure illustrates an example of the relation of thenon-elastomeric and elastomeric ground yarns as following the same paththrough the knit but not being plated so as to have the elastomeric yarnalways lie on one side of the fabric or the other. Rather, as shown, theyarn positions will shift from front to back throughout the ground, dueto movement of the yarns within the carrier plate ground feed hole.Using yarns of similar weights can exacerbate this effect. Heavierweight yarns will tend to migrate to the technical face if mixed withfiner weight yarns.

FIG. 4 shows the path of each yarn through the knit structure of thefabric, and shows how the pile yarn 44 is knit alongside the spandex 40and nylon 42 ground yarns, except that the pile yarn 44 is knit oversinkers to form a three-dimensional pile loop extending out of the planeof the ground. The material is knit to 32-34 wales per inch, asfinished. Other wale counts can be obtained by changing the machinegauge or by stretching in finishing. As stabilized with an elasticacrylic binder as discussed below, first fabric layer 12 has a basisweight of about 6.9 osy (230 gsm). Although schematically illustrated inFIG. 1 as a flat surface, it can be seen from FIG. 2 that the outersurface of the knit fabric has the characteristic undulations of a knitstructure from which the loop fibers extend. The fibers forming loops 16should be of sufficient strength to function through repeated hookcycling, so that they are not easily broken when engaged with a hook,resulting in an objectionably worn (frayed) appearance. For a long-use(i.e., non-disposable) product the fiber denier should be selected to bemuch coarser than yarns and fibers used in second fabric layer 20. Thereare numerous yarn and filament combinations possible, but as a practicalmatter commercial choices are normally limited to products that arecurrently available in volume. Yarns as large as 280/14 are commerciallyavailable, as well as yarns in the 200/10 range. Commercially availableyarns as small as approximately 15/1 (i.e., monofilaments) can be used,and yarns as small as 20/5 are possible. Another particularly suitablepile yarn is a 140/24 nylon. Finer denier fibers can be used if thefibers are of sufficiently high tenacity. Fibers of approximately 4grams/denier break strength are considered normal tenacity, while fibersof 8 grams/denier or more are considered high tenacity.

The nylon ground yarns are texturized with a false twist texturizingmethod, such as by heating and twisting the yarns between two surfacesduring yarn manufacture. When relaxed, the yarn has substantial bulk andtexture, and skein shrinkage of about 46 percent, as measured inaccordance with ASTM D4031. Other texturizing methods include frictiontexturizing, nip twisting, air jet texturizing, knit-de-knit, edgecrimping and gear crimping. Excessive texturizing can cause undesiredkinking of the yarn. The nylon ground yarn is preferably texturized toskein shrinkage of between about 30 and 55 percent. During knitting, thetension on the texturized ground yarns is limited to maintain a desiredlevel of texture or bulk. In this example the tension maintained on boththe nylon and spandex ground yarns is 6 grams. A suitable texturizednylon ground yarn is available from Sapona Manufacturing Company, Inc.of Cedar Falls, N.C., as product code 08020.1. In some cases the pileyarn is also texturized, either to add randomization or density to thepile or to increase the stretchability of the fabric. Texturized pileyarns may require less or no napping for disorientation.

The knit nylon/spandex fabric tube is placed in a pressure vessel andheat set under pressure in the presence of an anionic liquid dye thatreacts with amino groups of the nylon to form an ionic bond, the dyepenetrating through the nylon to affect its molecular weight. Heatsetting and dyeing may also be done at atmospheric pressures.

After heat-setting and dyeing, the knit tube is removed from thepressure vessel, slit open along its length, and treated with acommercial napping lubricant or fabric softener to facilitate napping.The slit fabric is then dried on a tenter frame or drum dryer (or othersuitable dryer), and then napped to raise the loops of the pile forbetter hook engagement properties. Special precautions should be takento prevent damage to the fabric when brushing or napping, due to thepresence of elastomeric yarn. In a brushing or napping operation, if thespandex is contacted by the brush or napper wire, it can be cut ordamaged. The knit fabric is then back-coated with a stretchable acrylicapplied to the technical face of the product as a foam emulsion thatbreaks down to wick the acrylic into the ground of the fabric to serveas a binder to stabilize the pile loops for increased pull-outresistance and cycle life. In order to retain the stretch/recoveryproperties of the fabric, the back coating should be of a material andan application mode that does not significantly hinder stretching thefinal fabric. Using an elastomeric binder material can in some casesimprove the resilience of the fabric even as compared to similarlyconstructed fabrics without a binder coat. A suitable elastomericemulsion that can be applied as a foam is HyStretch® V-43, availablefrom Lubrizol Advanced Materials, Inc. of Cleveland, Ohio. The V-43material is mixed with water at a ratio of 1.6 liters V-43 to 1.0 litersof water in a mixer that foams the mixture by air injection at avolumetric blow ratio of 20 parts air to 1 part liquid. Other blowratios as low as 3 to 1 are possible, depending on the density of foamdesired. The amount of the dispersion applied can be controlled toincrease or decrease the coat weight. Also, the mix ratio can be alteredto achieve the desired results of binding and tie coating. In some caseswhere light coating is required, flow rates as low as 0.5 liter/min areapplied at a fabric speed of 28 yards/min (25 meters/min). In othercases, flow rates of up to 5.0 liters/min are applied at similar linespeeds. In some cases the back-coating is applied at a flow rate of 1.2to 1.6 liters per minute, while a flow rate of 2.6 liters per minute canprovide more bonding.

The binder should be selected to be compatible with the laminationadhesive in order to prevent poor lamination adhesion. Some commonback-coating liquids, such as acrylic and urethane binders, caninterfere with the bonding of co-polyamide or co-polyester hot meltadhesives. Back coating fabrics using co-polyamide or co-polyesterpowders may be done in a scatter coat application, resulting in acompatible binder coat that does not dramatically reduce airpermeability. In other cases, these powders can be dispersed in a pasteand applied in convention coating methods.

Back-coating powders may be dispersed in an acrylic or urethane binderto provide deeper penetration into the fabric than a hot melt. Thedispersed powders, because of their larger particle size, tend to filterout and remain on the outside surface of the fabric. In some casespowders are dispersed as one part powder to ten parts binder, and havebeen found to give an improved bond over straight acrylic or urethanes.The weight percentage of the powder can be increased to 50 percent, oreven higher, to improve tie coat results. In some cases powder level canbe increased high enough to provide bonding to other surfaces or fabricswhen reheated (such as for lamination by iron) without a secondaryapplication of bonding hot melt. In one example, 10 percent co-polyesterpowder was blended into the acrylic binder and applied as a foam at arate of 1.6 liters per minute at a line speed of 28 yards/min (25meters/min). Further details of foam binder coating and fabric finishingcan be found in U.S. Pat. No. 6,342,285, the contents of which areincorporated herein by reference. The final added weight percentage ofthe added binder in the finished fabric is between about 9 and 16percent.

The binder is applied to the technical face of the fabric, either justbefore or while the fabric is stretched on a tenter frame and passedthrough an oven to dry and cross-link the binder before relaxing thefabric. The applied stretch during cross-linking of the acrylic binderis not excessive, and is primarily to hold the fabric taut duringstabilization. In one example the fabric is stretched widthwise up toabout 15 percent, while being overfed into the tenter as much as 15 to20 percent in the lengthwise direction, to offset any residuallongitudinal tension from prior processing and to prevent loss ofelasticity. Tenter frame roll tension is also kept low. A greater amountof stretch during binder setting may increase breathability at someexpense of elasticity. The fabric is then dried and heat set on thetenter frame, at a temperature of 320 degrees Fahrenheit (160 degreesC.) for about 35 seconds, then spooled.

This nylon/spandex example of knit fabric 14 has a fabric stretch of 20to 34 percent, as tested per ASTM 6614-00 CRE method, with a recovery ofabout 97-98 percent.

Second fabric layer 20 is formed of hydrophobic, microdenier yarns andelastomeric yarns. By ‘microdenier yarns’ we mean yarns formed ofmicrodenier fibers. In this example, each filament of the yarns is ofabout 1.0 denier. Fabric layer 20 is a circular knit material, of abasis weight of about 4.8 osy (160 gsm). It is preferable that thenon-elastomeric yarn used in this fabric be of very fine fibers in thenear-microdenier or microdenier range, making it soft against the skinto improve comfort. It has been discovered that if fibers in these yarnsalso have irregular cross-sections, such as dogbone or cloverleaf, orare hollow, tiny spaces between or inside the fibers promote capillaryaction, helping to remove moisture from the skin. Hydrophobic polyesteryarns are desirable because of their low moisture content, but nylonfibers, in particular modified nylon or hydrophobic polypropylenefibers, can also be used. Additionally, these fibers may be producedwith silver compounds included in the polymer, for anti-microbialproperties. By adding these compounds into the fiber, or by topicaladdition to the finished fabric, bacterial growth can be controlled toreduce infection and prevent odor. In one example the yarns are suppliedby Hyosung of Korea, available under the brand name of Aerosilver®.Several yarns and filament counts are available under this brand name.In one example a 70/72 yarn is selected for both the pile yarn and oneground yarn, the other ground yarn being the same 70 denier monofilamentspandex yarn as in the example of first fabric layer 12, describedabove. As in that example, the spandex yarn is fed into the same feedhole as the non-elastomeric ground yarn, in every other carrier plate,such that the spandex and non-elastomeric ground yarns follow the samepath in the ground of the knit material but are both present on thetechnical face of the knit. The non-elastomeric polyester ground yarn isnot texturized, but the non-circular Aerosilver® yarns are found to havesome resiliency without post-texturization. Another suitable polyesteryarn configuration is a 150/144 Aerosilver® or Aerocool® yarn, alsoavailable from Hyosung.

The knit polyester/spandex fabric tube is placed in a pressure vesseland heat set under pressure in the presence of a dispersed dye thatpenetrates into the polyester but forms only a weak hydrogen bond. Areducing agent helps to remove dye from the surface of the polyester,particularly in darker shades. After heat-setting and dying, the knittube is removed from the pressure vessel, slit lengthwise, dried, andthen napped to break the pile fibers to create a surface with a desiredeffective coefficient of friction to maintain position against skin, forexample. No napping lubricant is needed as the intention of the nappingis to break the pile. The broken-pile fabric is then pinned on a tenterframe, dried and heat set at a temperature of 320 degrees Fahrenheit(160 degrees C.) for about 35 seconds, and then spooled. In some casesit may also be advantageous to apply a stretch binder coat to the backof the polyester/spandex fabric. While such a coating is not needed tolock in the pile, it can improve the elastic recovery, and provide acleaner cut edge to the laminate.

In the example described above, second fabric layer 20 is a circularknit fabric, but warp knit fabrics may also be employed. In someexamples, first fabric layer 12 is a warp knit fabric and second fabriclayer 20 is a circular knit.

Referring next to FIG. 5, both knit fabrics 14,30 are laminated togetherto produce the finished laminate 10. Hot melt adhesive 22 is applied tothe technical face of knit fabric 14 by a gravure printing process. Theadhesive is a heat-stabilized co-polyamide resin available from EMS asGriltex® D 1566A. It has a very high melting point, of about 240 to 257degrees F. (applied at a temperature of 150 degrees C. for decreasedviscosity), to enable the laminate to be stable through washing cycles.Alternatively, a co-PA/PET or co-PET resin may also be employed, as canmoisture cure adhesives and adhesives other than hot melts. The adhesiveis applied as discrete dots, in a pattern resulting in an averagedistribution of 28 gsm of adhesive, such that the adhesive comprisesonly about six percent of the final laminate weight. Higher adhesiveapplication weights, such as 57 gsm, may be appropriate for someapplications. This glue produces a good bond between two dissimilarsurfaces. Other hot adhesives can be employed, such as polyamide,polyester or polypropylene. The technical face of fabric 14 contacts arotating gravure roller 44 that leaves discrete dots of molten adhesive22 on the technical face of the fabric, by known gravure printingmethods. The technical faces of both fabrics may be heated, such as byinfrared heaters 46, just before entering a lamination nip 50 definedbetween pressure roller 48 and laminating roller 52, where sufficientpressure is applied to form the laminate. Suitable lamination equipmentmay be obtained from Lacom Vertriebs GmbH Laminating Coating Machines ofLauchheim, Germany.

Gravure roller 44 has an outer surface that defines a pattern of offsetor random cavities that each carries an associated, discrete volume ofadhesive to the fabric surface. The pattern may comprise dots or lines,for example. With an offset or random dot pattern, adhesive dots areoffset or random to distribute the bonding strength evenly. With alinear dot pattern the adhesive dots are arranged in lines, and indelaminating the products this can be felt as a bond-no bond force. Thepatterned adhesive application creates spaces between the adhesive dotsfor air to pass. Dot pattern, diameter, density, cavity depth, etc, allinfluence the percentage of coverage of adhesive on gravure roller 44and in the final lamination 10. This can also be influenced by the useof a negative or positive doctor blade position. Gravure rollers 44 areavailable to provide coverage of 10 to 70 percent, and custom patternsare available.

It is possible to improve the adhesive bond while still obtaining a goodpermeability by changing the depth of the gravure dot cavities. A deeperdot holds more volume of adhesive, and creates a taller mound ofadhesive to bridge the spacer layer between the two fabrics beinglaminated. Cavity depths of 0.06 mm to 0.50 mm are available.

Line speed and temperature are important factors to control the laminatebond strength, particularly with gravure rollers 44 that deposit lessadhesive, such as a CP 100 or CP 96 gravure roller. Slower line speedsof approximately 5.0 yards/min (4.5 meters/min) or less can improve thebond with these lower-adhesive rollers. Using gravure rollers 44 thatdeposit more adhesive, bond strength is increased at higher speeds.Preferably lamination occurs while the adhesive is still somewhatflowable. More gravure adhesive lamination details can be found inpending U.S. patent application Ser. No. 12/750,887, published asUS-2010-0247846-A1, the entire contents of which are hereby incorporatedby reference.

Following lamination, the laminate is then passed over a chilled roll 54and the laminate edges may be trimmed in line as the laminate is beingwound onto a roll. In some cases, the edge is trimmed in a separateprocess on suitable equipment designed for this purpose. It is preferredto trim outside edges that do not receive adhesive, and therefore areunbound. The laminate is then spooled for transportation or furtherprocessing.

The adhesive may be applied by other means. For example, a web adhesiveor apertured film, such as available from DelStar Technologies, Inc. ofMiddletown, Del., USA can be used. These webs can be formed by a randomspray pattern, embossed from a film, or formed on a laminating machinewith a gravure roll to form an open web, which can then be fed betweenthe two fabrics into a heated belt laminator. In other cases breathablelaminates can be formed by ultrasonically bonding multiple layers offabric using little or no adhesive in the laminate. Beckmann ConvertingInc. of Amsterdam, N.Y., USA is capable of doing such ultrasoniclamination. Another means is scatter or powder coating, in which ahot-melt resin is sprinkled on a moving web as a powder, heated to meltthe resin, and then nipped with the other fabric to bond the web andfabric together to form the laminate. In some cases, when adhesive isapplied by any method, such as gravure, powder, spray, or web adhesivefilm, the two fabrics are compressed together with light pressure withheat on a belt laminator, so as to provide bonding without crushingsurfaces of sensitive fabrics.

Mechanical methods of securing the two fabrics together, as analternative to, or in addition to, adhesive, include needling orstitch-bonding the two fabrics together. Ultrasonic heat staking isanother bonding means, which can create a quilted surface.

Laminate 10, as formed, preferably has a basis weight of less than about20 osy (675 gsm), or in a range of 10 to 20 osy (335 to 675 gsm). Oneexample had a basis weight of 17.5 osy (590 gsm). Adhesive laminationbond strength can also be measured on an Instron tester in accordancewith the ASTM D 2724-03 test method.

Laminate 10, as formed, preferably has an air permeability, measured inaccordance with ASTM D737-04, of at least 40 cfm per square foot (12meters/min), more preferably at least 75 cfm per square foot (22meters/min). Air permeability may be measured on a Frazier AirPermeability Instrument, model FAP-HP, supplied by Frazier PrecisionInstruments Co Inc. of Hagerstown, Md., USA.

Laminate 10 is fashioned to have significant in-plane resilience orstretchiness, in both machine and cross-machine directions, due in partto the inclusion of elastomeric fibers or yarns to both fabrics. Suchfibers may be formed of a polyurethane polymer known as elastane orspandex. Spandex is extruded as a monofilament in round or shapedcross-section, and is available as a multifilament with a denier as lowas 15. Increasing the denier of the spandex increases the “power” ofelastic recovery. In some medical applications like elastic bandages,more power is desired to provide compression in the bandage.

Laminate 10 is also configured to provide particularly high frictioncoefficients at the skin contact surface, while at the same timeproviding a non-tacky, fibrous skin contact surface. In the case ofmedical textiles that are worn in direct contact with the skin, highercoefficients of friction help the material to stay in place as thewearer moves, while the material itself should be soft enough to preventdermal abrasion. By “kinetic friction coefficient” and “static frictioncoefficient” I mean the friction coefficients as determined inaccordance with ASTM D1894-01, with the laminate secured to a rigidsurface such that the skin contact surface of the laminate is facingupward for direct contact with the 63 mm by 63 mm square underside ofthe 200 gram sled, which is of stainless steel and has an undersidesurface roughness of 15-18 micro-inch (0.40-0.45 μm). Using that method,one example of the laminate discussed above exhibited a static frictioncoefficient of about 0.42, and a kinetic friction coefficient (with thesled pulled across the laminate at a constant speed of 150 mm/min) ofabout 0.36. Preferably, the laminate has a static friction coefficientof at least 0.4, and a kinetic friction coefficient of at least 0.25, orin some cases at least 0.3.

In an example of a disposable, three-part laminate (not illustrated), anelastomeric core, such as a stretchable nonwoven or knit fabric or scrimor porous film, is laminated between a skin-friendly material ofhydrophobic and antimicrobial properties, and a hook-engageable fabric.A lightweight, hook-engageable material is laminated to the oppositeside of the stretchable core layer. As with the two-part laminatediscussed above, sufficient adhesive may be applied to a given, discretearea to cause the adhesive to penetrate through the core and directlybond the outer fabric layers to one another.

The stretchable knit pile fabrics discussed above may be knit on astandard circular knitting machine equipped to feed the three distinctyarns from different spools. FIGS. 6 and 7 show one of a series of yarncarrier assemblies spaced about the rim of a circular knitting machineon which the fabric is formed. The carrier assembly 60 carries a yarncarrier plate 62 that receives the three yarns from their respectivespools (not shown) via positive yarn storage feeders, and directs themsequentially to a series of needles 64 that are raised by a cam systemwith respect to the carrier plate. The ground yarns (elastomeric yarn 40and texturized non-elastomeric yarn 42) are separately fed to a singleground yarn feed roller 66, where they are joined and fed into a groundfeed hole 68 in the top surface of the carrier plate. Pile yam 44 is fedthrough a grommet 70 and into a pile yarn feed hole 72 in the sidesurface of the carrier plate. While the two ground yarns emerge togetherfrom ground feed hole 68 at the bottom of the foot of the carrier plate(see FIG. 8), the pile yarn 44 passes out the back side of the carrierplate and is knit into the material over a series of sinkers (not shown)to form the pile.

The elastomeric and non-elastomeric ground yarns are not normally joinedin the carrier plate in typical stretch jersey knit materials. Rather,the elastomeric yarn is typically fed into a separate groove 74 thatruns down the foot of the carrier plate (see FIG. 8) in this style ofcarrier plate, such that at the lower end of the carrier plate foot thetwo ground yams exit always with a fixed relative positioning, with theresult that the non-elastomeric yarn is consistently placed on thetechnical face of the fabric, while the elastomeric yarn will begenerally trapped between the technical face yarn and the pile yarn.Because in this example the two ground yarns are fed through the samefeed hole, they will tend to shift in their relative positioning duringknitting, with the non-elastomeric yarn occasionally lying on thetechnical face, and the elastomeric yarn occasionally lying on thetechnical face. Because of this knitting method, both ground yarns willbe present on the technical face, as illustrated in FIG. 3.

By changing yarn position between hole and slot, the elastomeric yarncan be either positioned to be covered by the non-elastomeric yam orpositioned to be more exposed on the technical face of the knit fabric.By placing the elastomeric yam in the slot, it will tend to be coveredby the non-elastomeric yarn. If the elastomeric yarn is placed in thehole and the non-elastomeric yam is placed in the slot, more of theelastomeric yam will plait to the technical face. Carrier plates ofMayer knitting machines do not use a slot, but instead have 2 holes.

Feeding the elastomeric yarn through groove 74 will cause theelastomeric yarn to be exposed on the technical face in greaterproportion than the non-elastomeric yarn. This may be particularlyuseful in laminating two such fabrics together with an adhesive thatbonds two elastomeric surfaces together well. It may be that someurethane or acrylic adhesives will have better chemical affinity with asegmented polyurethane spandex surface, for example, than with a nylonor polyester surface, thereby efficiently and permanently bonding suchspandex-backed materials together to form a laminate. Development of astrong chemical bond with the adhesive may help to reduce the bondingsurface area required for reliable lamination, further increasing theobtainable air permeability of the laminate.

FIG. 9 shows how little adhesive may be necessary to effectively bondtogether two fabrics knit to have both elastomeric and non-elastomericyarns exposed on their technical backs. In this enlarged sidephotograph, two discrete adhesive bonds are visible, corresponding totwo discrete dots of adhesive applied by gravure printing duringlamination, as discussed above. The adhesive shows up as lighter regionsin the photograph, with one visible near the left of the photographbetween the ground layers, and one near the right of the photograph. Theadhesive is in intimate contact with, and encapsulates portions of,fibers of the technical faces of both fabrics.

While a number of examples have been described for illustrationpurposes, the foregoing description is not intended to limit the scopeof the invention, which is defined by the scope of the appended claims.There are and will be other examples and modifications within the scopeof the following claims.

1. A flexible, breathable, stretchable fabric laminate, comprising afirst stretchable fabric layer in the form of a first knit fabriccomprising ground yarns and pile yarns forming hook-engageable fiberloops exposed on an outer surface of the fabric laminate, and atechnical face at which both portions of ground yarns and portions ofpile yarns are present; and a second stretchable fabric layer bondeddirectly to the first fabric layer by an adhesive that covers less thanan entire area of either fabric layer, leaving adhesive-free areas ofthe laminate, the second fabric layer in the form of a second knitfabric comprising both ground yarns and pile yarns and having atechnical face at which both portions of ground yarns and potions ofpile yarns are present; wherein at least one of the first and secondknit fabrics comprises a circular knit fabric; wherein the ground yarnsof the first knit fabric and the ground yarns of the second knit fabriccomprise elastomeric yarns; and wherein the first and second fabriclayers are bonded together at their technical faces, such that theadhesive is in contact with both pile yarns and elastomeric ground yarnsof each knit fabric.
 2. The fabric laminate of claim 1, wherein both thefirst and second knit fabrics are circular knit fabrics.
 3. The fabriclaminate of claim 1, wherein the first knit fabric is relatively morehydrophilic than the second knit fabric.
 4. The fabric laminate of claim1, wherein the ground yarns of the first knit fabric include bothelastomeric yarns and texturized, non-elastomeric yarns.
 5. The fabriclaminate of claim 4, wherein each elastomeric yarn follows a common paththrough the first knit fabric with a corresponding texturized yarn. 6.The fabric laminate of claim 4, wherein the elastomeric yarns arenon-wrapped yarns.
 7. The fabric laminate of claim 4, wherein thetexturized, non-elastomeric yarns are also present at the technical faceof the first knit fabric.
 8. The fabric laminate of claim 1, wherein thelaminate has a basis weight of less than about 16 osy (675 gsm).
 9. Thefabric laminate of claim 1, wherein the laminate, as formed, has an airpermeability measured in accordance with ASTM D737-04, of at least 40cfm per square foot (12 meters/min).
 10. The fabric laminate of claim 1,wherein the ground yarns of the first knit fabric include texturizednylon yarns and the ground yarns of the second knit fabric includetexturized polyester yarns.
 11. The fabric laminate of claim 1, whereinthe first stretchable fabric layer comprises a stretchable binder withinthe ground of the first knit fabric.
 12. The fabric laminate of claim 1,wherein the second fabric has an exposed skin contact surface configuredto provide a kinetic friction coefficient of at least 0.3.
 13. Thefabric laminate of claim 1, wherein the adhesive covers no more thanabout 70 percent of either fabric layer.
 14. A method of forming abreathable fabric laminate from fabrics of differing properties, themethod comprising providing first and second knit fabrics havingtechnical faces at which portions of both pile fibers and elastomericground fibers are present, one of the fabrics being relatively morehydrophilic than the other fabric and at least one of the fabrics beinga circular knit fabric; applying an adhesive to the technical face of atleast one of the knit fabrics such that the adhesive occupies no morethan about 70 percent of the area of the technical face to which it isapplied; and then bonding the technical faces of the fabrics together toform a breathable laminate.
 15. A flexible, stretchable fabric laminatecomprising a first stretchable fabric layer in the form of a knit fabriccomprising ground yarns and pile yarns forming hook-engageable fiberloops exposed on an outer surface of the fabric laminate; and a secondstretchable fabric layer bonded directly to the first fabric layer by anadhesive; wherein the knit fabric is a circular jersey knit fabric. 16.The fabric laminate of claim 15, wherein the adhesive covers no morethan about 70 percent of either fabric layer, leaving adhesive-freeareas of the laminate.
 17. A method of forming a circular knit pilefabric, the method comprising feeding a multi-filament non-elastomericyarn from a first spool into an aperture defined in a yarn carrier platethat guides the non-elastomeric yarn sequentially to a series ofknitting needles spaced about a circular needle array; while feeding anelastomeric yarn from a second spool to the yarn carrier plate, suchthat a fabric is knit to have a ground comprising both thenon-elastomeric yarn and the elastomeric yarn; while feeding a pile yarnfrom a third spool into a pile yarn aperture defined in the carrierplate, such that the pile yarn is delivered to the knitting needles toform a pile extending from a technical back of the knit fabric; whereinthe elastomeric yarn is fed to the carrier plate such that the fabricground is knit to have a technical face, opposite the pile, in which theelastomeric yarn is exposed in greater proportion than thenon-elastomeric yarn.